Purgatives (laxatives or cathartics) are widely used as self medications to satisfy the patient's desire for an altered or more regular bowel habit. They are also used for bowel clearance before radiological examination, surgery, or childbirth. Purgatives used in the treatment of functional constipation include phenolphthalein, senna, cascara, bisacodyl, and sodium picosulfate. Salts of inorganic acids which are not extensively absorbed from the gastrointestinal tract, such as sodium phosphate, retain water in the lumen of the bowel by an osmotic effect and are also used as purgatives. Prolonged use of purgatives may produce excessive loss of water and electrolytes, particularly potassium. A commonly used oral lavage solution is Fleet's concentrated phosphosoda solution which is manufactured according to the National Formulary monograph for Sodium Phosphates Oral Solution. This product, as described in the National Formulary (USP 23/NF 18, p. 1430), contains disbasic sodium phosphate and monobasic sodium phosphate or phosphoric acid in water. The marketed product, which claims a ginger-lemon flavor, in fact, has a very strong salty and sour taste. No other flavoring is evident, even as an aftertaste.